Process and apparatus for modifying the cross section of a slab

ABSTRACT

There is disclosed a method and an apparatus for modifying the cross section of a metal slab, which may be a continuously cast slab coming from a caster, to prepare the slab for reduction to strip in a cyclic mill, e.g. a planetary mill. The slab is advanced at constant speed by independent means, while pairs of pressing tools are caused to operate on all four sides of the slab in repeated and coordinated reciprocating action. The thickness of the slab may be reduced as much as 70%, and the width may be maintained constant, or increased, or decreased as desired. The frame of the apparatus carries the shaft driven by suitable means; and the shaft has two pairs of eccentrics oriented at 180* to each other. Each pair of eccentrics actuates a pressing tool, one operating on the top of the slab, and one operating on the underside of the slab. As the pressing tools thus reciprocate they act on opposite sides of the slab to reduce its thickness. The tools are arranged for a slight rocking movement so that they do not retard the forward movement of the slab. Other tools are arranged in pairs to operate on opposed sides of the slab in a similar manner. For substantial widening of the slab the pressing tools may be disposed at an angle to the centerline of the entering slab.

United States Patent [191 Sendzimir 1 Nov. 25, 1975 PROCESS AND APPARATUS FOR MODIFYING TI-IE CROSS SECTION OF A SLAB [76] Inventor: Tadeusz Sendzimir, PO. Box 1350,

Waterbury, Conn. 06720 [22] Filed: Apr. 11, 1974 [21] Appl. No.: 459,900

[52] US. Cl. 72/189; 72/225; 72/406 [51] Int. Cl. B21]! 13/18 [58] Field of Search 72/189, 190, 225, 402, 72/403, 404, 406, 407, 408

[56] References Cited UNITED STATES PATENTS 3,213,661 10/1965 Sendzimir 72/190 3,415,106 12/1968 Lauener 72/408 3,427,851 2/ 1969 Michelson.. 72/408 3,439,519 4/1969 Gerding 72/189 3,460,370 8/1969 Kralowetz 72/408 3,596,497 8/1971 Kralowetz et a] 72/404 FOREIGN PATENTS OR APPLICATIONS 1,073,231 9/1954 France 72/189 'Primary Examiner-Lowell A' Larson Attorney, Agent, or Firm-Melville, Strasser, Foster &

' Hoffman [57] ABSTRACT There is disclosed a method and an apparatus for modifying the cross section of a metal slab, which may be a continuously cast slab coming from a caster, to prepare the slab for reduction to strip in a cyclic mill, e.g. a planetary mill. The slab is advanced at constant speed by independent means, while pairs of pressing tools are caused to operate on all four sides of the slab in repeated and coordinated reciprocating action. The thickness of the slab may be reduced as much as 70%, and the width may be maintained constant, or increased, or decreased as desired. The frame of the apparatus carries the shaft driven by suitable means; and the shaft has two pairs of eccentrics oriented at 180 to each other. Each pair of eccentrics actuates a pressing tool, one operating on the top of the slab, and one operating on the underside of the slab. As the pressing tools thus reciprocate they act on opposite sides of the slab to reduce its thickness. The tools are arranged for a slight rocking movement so that they do not retard the forward movement of the slab. Other tools are arranged in pairs to operate on opposed sides of the slab in a similar manner. For substantial widening of the slab the pressing tools may be disposed at an angle to the centerline of the entering slab.

9 Claims, 13 Drawing Figures U.S. Patnt N0v.25, 1975 Sheetl0f4 3,921,429

[ @VQE US. Patent Nov.25,1975 Sheet2of4 3,921,429

FIG. I0

U.S., Patent Nov. 25, 1975 Sheet4 of4 3,921,429

PROCESS AND APPARATUS FOR MODIFYING THE CROSS SECTION OF A SLAB BRIEF SUMMARY OF THE INVENTION A slab of steel or other metal emerging in an uninterrupted length from a continuous slab caster has a substantially uniform cross section and quite a long shutdown is necessary in order to change the mold of the caster to produce a different cross section, or even to change the width of the slab in the same mold.

A direct cast slab is hot enough for direct rolling into strip on a planetary mill or the equivalent, but up to now it has been impractical to install such a rolling mill directly in line with the caster for two reasons. First, orders for strips usually call for many different widths and gauges; and second, cast slabs are usually too thick for direct introduction into a planetary or equivalent hot strip mill.

The present invention provides a process and an apparatus for continuously modifying the section of such a slab while on its way from the caster through the heat equalization chamber and into the planetary mill. Such modification may reduce the thickness of the slab by as much as 70% while either reducing, increasing, or maintaining the width of the slab.

The process involves passing a direct cast, uniform section hot slab through a configuration of pressing tools, which act in coordinated succession on all four faces of the slab as it advances, and prior to its entry into the feed rolls of a suitable hot strip mill. The pressing tools gradually modify the section of the slab to a section required by the mill to produce a strip of the desired dimensions. The hot strip mill is preferably a socalled cyclic mill (for example, a planetary mill) where the advancement of the slab is controlled by feeding means such as feed rolls which are independent of the cycling work rolls. Cyclic mills can reduce the slab right down to strip gauges in a single pass which makes it possible to complete the hot deformation at a sufficiently high temperature.

One characteristic of the configuration herein disclosed is that by alteration of the position of the tools with respect to the slab, the dimensions of the modified slab can be changed rapidly and within wide limits. With suitable controls it can be done almost instantaneously in most cases.

According to the invention, the forging tools are mounted on their prime movers so as to be rigid in the direction in which they penetrate the work piece, but flexible in the direction of travel of the latter. Thus, they do not impede the forward progress of the slab which is being fed forward into the planetary mill by the feed rolls of the planetary mill at a substantially uniform velocity. Thus each working stroke of each of the tools consists of an advancement toward and into the slab, accompanied by a slight rocking of the tool about its axis to provide the above noted flexibility.

Each tool is provided with means to adjust its point of first contact with the work piece. The more the direction of tool pressure is inclined from normal in the direction of slab travel, the bigger the component of tool pressure tending to push the slab forward, i.e. in the same direction as the feed rolls. At the same time, the simultaneous rocking action of the tool consumes energy acting in the opposite way. Because of the rapid succession of pressing strokes by said tool in relation to slab velocity, the rocking angle is small, usually only 1 2 or 2. It is therefore easy to adjust the point of engagement of each tool such that the force exerted by it axially upon the slab is rather in the direction of advancement of the slab, so as very slightly to reduce the torque demand on the feed rolls.

Since each tool engagement causes the slab to elongate, and consequently to retard its entering speed, (the exit speed being dictated by the planetary feed rolls, as explained above) the strokes of the plurality of tools are timed so as to spread them into a plurality of small retardations which will have no adverse effect upon the operation of the caster, and which will be small enough individually to be absorbed by the elasticity of the following length of slab.

for the same purpose, there is provided a tool drive to be used in the case of some difficult metals, which causes the tool to penetrate slowly into the slab and to return more rapidly, to further reduce inductions of slab velocity.

Furthermore, according to the invention the cooling of the tools is preferably by internal circulation of a fluid, and is so controlled that the working faces of the tools are at or near the highest permissible temperature in order to withdraw the least heat from the slab and preventing excessive wear of the tools, while the deformation energy absorbed by the slab further protects it from heat loss through radiation and convection.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1 is a somewhat diagrammatic cross sectional view of an apparatus according to the invention showing opposed tools for operating on the upper and undersides of a slab.

FIG. 2 is an elevational view, partly in cross section, of FIG. I as seen from the right, with the feed rolls removed.

FIG. 3 is a fragmentary view of the same in plan, with parts in cross section, showing a pair of opposed tools for operating on the sides of the slab.

FIG. 4 is a fragmentary view similar to FIG. 1 showing a modification.

FIG. 4a is a cross sectional view taken on the line 4a-4a of FIG. 4.

FIG. 5 is a diagrammatic representation of another modification.

FIG. 6 is a diagrammatic view in elevation, showing the exit end of a continuous caster and a planetary mill, and showing the relationship thereto of the apparatus of the present invention.

FIG. 7 is a plan view ofFIG. 6.

FIGS. 8, 9 and 10 are diagrammatic plan views showing various orientations of the apparatus for the production of a slab which is wider than the continuously cast entering slab.

FIG. 11 is a fragmentary plan view with parts in cross section of another modification; and

FIG. 12 is an elevational view of the same with parts in cross section. DETAILED DESCRIPTION A simple arrangement of tools in an apparatus with which the present process may be practiced and where the requirements for modification of the slab cross section are modest, is shown in FIGS. 1, 2 and 3. In these Figures, a continuous length of cast steel slab 1 advances from the heat equalization hood and is gripped by pinch rolls 2 and pass successively through the bite of the edging tools 3 and the reducing tools 4 and the 3 slab emerges in modified form as indicated at 1 and passes into the feed rolls of the planetary mill.

The edging tools 3 and the reducing tools 4 all operate from a common shaft as will now be explained. The shaft 7 is mounted in bearings 8, 8 disposed in the housing 13 and is driven at constant speed by the gear 6. The upper tool 4 is mounted in the U-frame 11 which is actuated by the eccentrics and 10 while the lower frame 12, which carries the lower tool 4, is actuated by the eccentrics 9, 9 which are oriented at 180 to the eccentrics 10 and 10. It will be seen that as the shaft 7 rotates, the tools 4 will be caused to reciprocate toward and away from each other in a rapid sequence. In order to assure a uniform starting point for the tools 4 at each stroke, there is provided a rod 14 which is fulcrumed in the frame 11 of the upper tool 4 at one end, and in the column of the planetary mill 15 at the other end. This connecting rod includes an air loaded cylinder with an adjustable stop to assure that both tools 4 when they converge upon the slab 1 will always make their contact with the work piece while in a certainangular position with respect to the eccentric shaft 7. Once this contact is made, both frames 11 and 12 are free to swing carrying the respective tools 4 around the shaft 7 while they are penetrating into and therefore reducing the thickness of the slab 1. As a result, the grip of the tool 4 on the slab 1 does not interfere with the forward progress of the reduced slab 1 which must move at the velocity imposed upon it by the feed rolls 5 of the planetary mill.

The edging tools 3 are mounted on connecting rods 22 and 22 respectively, and these connecting rods are suitably fulcrumed in pistons 21, 21 so that these tools may also follow the movement of the slab 1 during their operating contact with it without impeding the movement of the slab. The pistons 21, 21' operate in cylinders 20, which are connected with pumps l9, 19 which in turn are actuated by connecting rods 17, 17 connected to cranks 16, 16' mounted on the ends of the shaft 7. The hydraulic connections are only shown.

schematically since the details thereof will be obvious to one skilled in the art and are not necessary to an understanding of the present invention.

With the apparatus of FIGS. 1 to 3, reductions in thickness as high as 50% are easily obtained by the tools 4 engaging the flat faces of the slab 1. However, the reduction in width of the slab. produced by the edging tools 3 are generally only sufficient to correct the width of the slab l and if necessary to make a reduction of a few percent.

In the modification of FIG. 4, the press housing 13 carries two parallel single eccentric shafts 7, 7 which reciprocate the tools 4 and 4' which are mounted in the frames 12 and 12'. The tool 4 is opposed by a stationary anvil 4a while the tool 4' is similarly opposed by a stationary anvil 4a. This arrangement splits the reduction of the slab 1 into two smaller reductions which are set at 180 from one another by suitable gearing and thereby reduce the fluctuations of the slab speed at the entry into the press.

A further reduction of these fluctuations may be obtained by substituting elliptical gears for circular gears I as diagrammatically shown in FIG. 5. Here the shafts 7,

7 are driven at a lower angular speed when their respective tools are in operating contact with the slab l and at high relative speeds when they are out of contact with the slab. This is accomplished by substituting for the circular gears 6 of FIG. 2 the elliptical gears 6, 6'

which are keyed onto the shafts 7, 7 and rotate around their centers. These gears are in mesh with other elliptical gears 6a, 6a mounted and keyed onto the countershafts 7a and'7a and which rotate around one of their foci. A drive is applied to one of the countershafts 7a which has a circular pinion 6b keyed thereon for transmission of torque to the shaft 7a through the pinion 6b keyed to shaft 7a. I

In FIG. 6, 51 indicates the supporting rolls and 52 the straightening rolls at the end of the conventional continuous casting unit. 26 indicates a heat equalization hood or furnace in which to assure complete solidification of the metal and to insure that a uniform forging temperature is achieved. A planetary mill is indicated at 27 having the feed rolls 5 and the apparatus of the present invention is shown to be between the heat equalization furnace and the planetary mill. In this particular instance there are shown two sets of edging presses 63 and 63'. The slab coming from the continuous caster is shown at 1 and the slab in its modified cross section entering the planetary mill is shown at l and the strip emerging from the planetary mill is indicated at 1'.

With the arrangement of FIGS. 6 and 7, slab width can be reduced by as much as thirty or more percent while the slab thickness may be reduced by fifty percent. Any intermediate reductions can be obtained by simple and rapid adjustment of the several tools acting upon the slab.

If it is desired to produce slabs that are wider than the entering continuously cast slab, a configuration of tools as shown in FIGS. 8 and 9 may be adopted. Here only one pair of edging presses 63 is used to produce the minimum amount of edge working compatible with the sound metal structure. Here the thickness reducing press 64 is installed at an angle to the path of the slab 1. Since the direction in which the slab is fed into the press 64 is the same as the path of the slab 1 but the elongation produced by the press 64 is at right angles to the axis of the tools (assuming a 50% reduction), the resulting path of the slab 1 will be halfway between the two as shown in FIG. 8. This produces a first widening of the slab. The slab 1 may be further reduced by a second press 64 which is installed on a turntable 55 and which is slidable along rails 56 along the axis of the slab 1'. In adjusting the angular position of the press 64', the bigger the angular deviation from the path of the entering slab l' and the bigger the thickness reduction, the wider will be the resulting slab la exiting from the press 64.

In order to feed the slab la into the planetary mill 27, the angle produced by the press 64' is adjusted to be in the opposite direction from the angle produced by the press 64. Since the slab la meets the path of the original slab at an angle, the feed rolls 5 of the planetary mill 27 are also made adjustable to the angle at which the slab 1a is entering, so that the slab 1a will enter the planetary roll bite with its axis intersecting the original axis of the slab (which is also the axis of the planetary mill) and the planetary mill, in reducing the slab laf changes its direction substantially back to the originali slab axis.

Itl should be noted that with the relatively slight angular deflection shown in FIG. 8, the issuing strip 1'' can be of the same width as the original slab l or slightly wider. With the configuration shown in FIG. 9, the widening of the slab may be as much as 50% and any increase in width in between can'be obtained by adjusting the position of the press 64 and the feed rolls only.

If it is desired to obtain still wider strips from the same slab sectiomthe same configuration of tools may be used except that the press 64 is adjustably mounted similar to the press 64'. However, if the angle of the press 64 is adjusted further away from the slab path in an endeavor to produce a still wider slab, it would be impossible to return the issuing slab 1 back to the path of the planetary mill with the press 64' alone. The angularity shown in FIG. 8 is about the maximum which is practicable.

However, the desired result may be obtained by adjusting the tools of the press 64 in its adjusted position so as to produce a slab 1 having a wedge-shaped cross section, i.e. elongating it more v at one edge than at the other. This results in the slab l in FIG. assuming a curved path, gradually changing its angle to one which the press 64 can accept and deliver the slab in into the'bite of the feed rolls 5 and into the center of the roll bite of the planetary mill 27 to produce the strip 1" which in this instance can be twice the original width of the slab 1. Again, any intermediate width and thickness can be produced practically without stopping the mill by a simple adjustment of the tools and their presses.

Thus, FIGS. 6 to 10 inclusive show various arrangements whereby relatively massive modifications of slab cross section are required, such as, for example, reducing the width of a slab by 25%, increasing its width by 25%, and/or reducing its thickness by 7 O%.The edging presses 63 and 63 of FIG. 6 are preferably operated separately so as gradually to reduce the width of the slab and thereafter the thickness reducing press 64 operates on the slab to produce a reduced slab 1 ready to enter-the feed rolls 5 of the planetary mill, which further reduces the slab to the strip 1'.

In order to obtain large reductions in the width of the slab while maintaining thickness substantially even from the edges to the center, it is preferred to use one or more presses such as shown in FIGS. 11 and 12. This press consists of the base 41 and two housings 42 slidably mounted in ways. Four screws 43 engage nuts 44 located in the housings and interconnected by chain driven sprockets 46 which control the distance and assure parallelism of motion of the two housings 42. At least one of the screws 43 is held axially by means of a thrust bearing 47 or the like in a bracket 48, so as to assure correct position of the press with respect to the center line of the slab l.

The pressing tool 30 is advanced and at the same time slightly rocked by the coaction of a forked connecting rod 31 which is driven by suitable means such as a shaft 49 carrying a worm 50, one for each edging tool holder 37. The worms 50 mesh with worm gears 54 keyed onto the eccentric shafts 33. The eccentric 35 on the shaft 33 engage the rod 31 while the eccentric 36 engages the rod 32. The other ends of the rods engage the tool holder 37 so as to advance the tool 30 toward and into the slab. The angular position of the rods 31 and 32 on the shaft 33 is slightly out of phase in order that one end of the tool 30 may advance slightly ahead of the other end and thus provide the rocking action mentioned heretofore. In order to adjust for optimum rocking action, the eccentric 36 is shrunk onto the shaft 33 so that its angular position on the shaft can be changed as needed.

Besides advancing and rocking the edging tool, the shaft 33 also serves as a fulcrum permitting the tool 30 to follow the speed of the surface of the slab 1 without exerting any substantial axial force thereon. This rocking action permits a reduction. of the tool pressure against the slab and makes it possible to obtain heavier reductions in width than would be possible with a nonrocking tool.

During the period when the tool 30is out of contact with the slab l, the spring 39 urges it against the adjustable stop gauge 40. This prevents the tool from swinging around the shaft 33 during its idle cycle and forces the tool to start its operating engagement with the slab at a predetermined angular position. The stop gauge 40 is preferably so adjusted that the average pressure angle of the tool 30 with relation to the shaft 33 is slightly ahead of normal to the slab I so that while the angle changes during the rocking of the tool 30, it exerts a slightly pushing rather than retarding force upon the slab 1, thereby reducing the torque demand of the planetary feed rolls 5 but never reversing it.

It will be clear that numerous modifications may be made without departing from the spirit of the invention, and therefore no limitation not specifically set forth should be implied and no such limitation is intended.

I claim: h

l. A press for forging slabs, said press having a. at least one pair of edge forming tools disposed to act normally on the edges of said slab,

b. means to reciprocate said tools rapidly,

c. means for rapidly adjusting said press, even during operation, for width of slab to beproduced, from a maximum width down to one-.halfsaidmaximum width, 7 I '1 1 d. and a pair of thickness reducing tools extending across the entire width of the slab, disposed down stream from said edge forming tools,

c. said last named tools being located in frames pivotally mounted on a vertical axis situated along the longitudinal axis of said slab, and

f. means for rapidly adjusting the angle of said last named tools with respect to the longitudinal axis of said slab.

2. A press according to claim I wherein said thickness reducing tools are provided with means to set them out of parallel, whereby to produce a slab of trapezoidal cross section, said slab therefor issuing from said press in a curved path.

3. A press according to claim 1 wherein a slide is provided to carry said pivoted frame and to locate the axis thereof, and means to rapidly adjust the position of said slide along the longitudinal axis of said slab.

4. An instrumentality for reducing the cross section of an uninterrupted slab being advanced at substantially constant speed by independent means, comprising at least one pair of edging tools for reducing the width of the slab wherein upper and lower pressing tools are provided downstream of said edging tools for reducing the thickness of said slab, and wherein the alignment of said upper and lower pressing tools may be shifted from an orientation normal to the centerline of said slab where widening of the slab is to be avoided, to an angular orientation with respect to said centerline where the slab is to be widened.

5. An instrumentality according to claim 4, in which two sets of upper and lower pressing tools are arranged in succession, the first set being oriented at an angle to the slab centerline, whereby the slab issuing from said first set of pressing tools has a new centerline at an angle to the original centerline of about one-half the 6. An instrumentality according to claim in combination with a planetary mill located on said original slab centerline and havin'g feed rolls, said feed rolls being adjustable about a vertical axis of symmetry of said planetary mill, whereby the said feed rolls may be aligned normalto the centerline of the slab issuing from said second set of pressing tools. to return the widened slab to its original centerline for any setting of said second set of pressingtools.

7. An instrumentality according to claim 6, wherein the tools of said first set are disposed at an angle to each other to produce a slab having a tapered cross section, and which will therefore follow a curve as it issues from said first set, with a thinner side of the taper being on the outside of the curve, whereby partially to direct said slab back toward its original centerline, said second setof pressing tools converting said tapered section back to a rectangular section which is thinner, and issuing from said second set in a straight line toward the saidfeed rolls, to be further widened by the resulting angular pass in the planetary mill.

8. In the production of hot-rolled metal strip ina variety of widths, from a slab of constant cross section issuing from a slab caster, in a substantial, one-pass reduc- 8 tion, on a planetary mill which requires for its starting material a slab of a lesser thickness and a variety of widths, the process of modifying the cross section of said slab which comprises reducing the thickness of said slab to 'a specified lesser thickness while either maintaining, increasing or decreasing its width, by

a. subjecting said slab to the repeated action of pair of opposed pressing tools, and I b. causing each tool always to engage the slab to a precise point along the slab in relation to the pivot axis of said tool, while c. leaving said tool free to follow the advancement of the slab, and

d. causing said tools to have a relatively slow working part of the cycle and a relatively fast idle part the average angularity of action of the tools creating a negligible forward pressure component, but exclusing any rearward component.

9. A press for reducing the cross section of a slab being advanced by independentrmeans, by the simultaneous action of pairs of tools acting on opposite sides of said slab, in which the tool'carrying frames are free to pivot around their crank axes while. the tools are in working engagement with said slab, and having an elastic element to urge them to rest against a fixed stop as soon-as they leave contact with said slab and until the next working engagement begins, the drive for said crank shaft including pairs of elliptical gears, keyed in position such as to reduce the angular velocity of the respective eccentric shafts during the part of the cycle when said tools are in working contact .with the slab,

and to increase its during the idle portionof the cycle. 

1. A press for forging slabs, said press having a. at least one pair of edge forming tools disposed to act normally on the edges of said slab, b. means to reciprocate said tools rapidly, c. means for rapidly adjusting said press, even during operation, for width of slab to be produced, from a maximum width down to one-half said maximum width, d. and a pair of thickness reducing tools extending across the entire width of the slab, disposed down stream from said edge forming tools, e. said last named tools being located in frames pivotally mounted on a vertical axis situated along the longitudinal axis of said slab, and f. means for rapidly adjusting the angle of said last named tools with respect to the longitudinal axis of said slab.
 2. A press according to claim 1 wherein said thickness reducing tools are provided with means to set them out of parallel, whereby to produce a slab of trapezoidal cross section, said slab therefor issuing from said press in a curved path.
 3. A press according to claim 1 wherein a slide is provided to carry said pivoted frame and to locate the axis thereof, and means to rapidly adjust the position of said slide along the longitudinal axis of said slab.
 4. An instrumentality for reducing the cross section of an uninterrupted slab being advanced at substantially constant speed by independent means, comprising at least one pair of edging tools for reducing the width of the slab wherein upper and lower pressing tools are provided downstream of said edging tools for reducing the thickness of said slab, and wherein the alignment of said upper and lower pressing tools may be shifted from an orientation normal to the centerline of said slab where widening of the slab is to be avoided, to an angular orientation with respect to said centerline where the slab is to be widened.
 5. An instrumentality according to claim 4, in which two sets of upper and lower pressing tools are arranged in succession, the first set being oriented at an angle to the slab centerline, whereby the slab issuing from said first set of pressing tools has a new centerline at an angle to the original centerline of about one-half the angle of said first set of pressing tools, the second set being mounted for linear adjustment on ways parallel to the original centerline of the slab, and oriented at an angle to the new centerline of the slab but in the opposite direction with respect to said first set, the angle of orientation of said second set being adjustable, whereby the slab, in widened condition issues from said second set at an angle directed back toward the original slab centerline.
 6. An instrumentality according to claim 5 in combination with a planetary mill located on said original slab centerline and having feed rolls, said feed rolls being adjustable about a vertical axis of symmetry of said planetary mill, whereby the said feed rolls may be aligned normal to the centerline of the slab issuing from said second set of pressing tools, to rEturn the widened slab to its original centerline for any setting of said second set of pressing tools.
 7. An instrumentality according to claim 6, wherein the tools of said first set are disposed at an angle to each other to produce a slab having a tapered cross section, and which will therefore follow a curve as it issues from said first set, with a thinner side of the taper being on the outside of the curve, whereby partially to direct said slab back toward its original centerline, said second set of pressing tools converting said tapered section back to a rectangular section which is thinner, and issuing from said second set in a straight line toward the said feed rolls, to be further widened by the resulting angular pass in the planetary mill.
 8. In the production of hot-rolled metal strip in a variety of widths, from a slab of constant cross section issuing from a slab caster, in a substantial, one-pass reduction, on a planetary mill which requires for its starting material a slab of a lesser thickness and a variety of widths, the process of modifying the cross section of said slab which comprises reducing the thickness of said slab to a specified lesser thickness while either maintaining, increasing or decreasing its width, by a. subjecting said slab to the repeated action of pair of opposed pressing tools, and b. causing each tool always to engage the slab to a precise point along the slab in relation to the pivot axis of said tool, while c. leaving said tool free to follow the advancement of the slab, and d. causing said tools to have a relatively slow working part of the cycle and a relatively fast idle part the average angularity of action of the tools creating a negligible forward pressure component, but exclusing any rearward component.
 9. A press for reducing the cross section of a slab being advanced by independent means, by the simultaneous action of pairs of tools acting on opposite sides of said slab, in which the tool carrying frames are free to pivot around their crank axes while the tools are in working engagement with said slab, and having an elastic element to urge them to rest against a fixed stop as soon as they leave contact with said slab and until the next working engagement begins, the drive for said crank shaft including pairs of elliptical gears, keyed in position such as to reduce the angular velocity of the respective eccentric shafts during the part of the cycle when said tools are in working contact with the slab, and to increase its during the idle portion of the cycle. 